200L (52 gallon) bags... good for long-term fruit trees?

I've discovered large, tough nursery bags (200 litres / 52 gallons) for growing trees are quite cheap, and easy to acquire by mail. $75 for 5, whereas half-wine barrels are $75 each and I can barely fit one in my car.

Nurseries sell mature trees in them. But do you think these can work long-term on the paving in my yard? I want to plant dwarf and semi-dwarf treess in them: red shahtoot mulberry, peach, persimmon, and maybe loquat.

Those bags are used to move trees into at around 5 years old, they can stay in them (heeled in with mulch on top of soil) for up to 10 years before the bags need to be replaced (this is in nursery conditions).

If you are going to set them on paving, there will be more heat getting to the roots which means less life span of both tree and bag.

The best way to use these in the setting you are describing would be to build a 2x4 frame larger than the bag and fill that with something like wood chips or wood mulch then plant you tree in the bag centered in the frame and build up mulch around the bag as high as possible.
This method will give you the ability to use the bag as long as possible before it breaks down.

I think it is a bang up idea.

Redhawk

I've seen a company in Australia marketing bags like this as an alternative to dwarfing root stocks.

I use a smaller bag (40 liters) for my own tree production.  

I've used them for up to 8 years with no degradation.

Gotcha1:  You should at least half bury the bag for stability.  Don't want it blowing over everytime the wind gets frisky.

Gotcha2: With the restricted root volume you have to be on top of watering, but a 40 liter bag will maintain an apple at about 1.25" caliper.

Gotcha3:  Eventually the sunlight on the bag will make it fall apart. Wrap the exposed part of the bag with a sacrificial layer.  The tarps that lifts of lumber come wrapped in work well for this.